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Mohamed Masoud KM, Syed SM, Alasiri AM. Analyte protectant approach to protect amide-based synthetic cannabinoids from degradation and esterification during GC-MS analysis. J Chromatogr A 2024; 1730:465022. [PMID: 38861824 DOI: 10.1016/j.chroma.2024.465022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2024] [Revised: 05/21/2024] [Accepted: 05/22/2024] [Indexed: 06/13/2024]
Abstract
The forensic analysis of amide-based synthetic cannabinoids (SCs) in seized materials is routinely performed using gas chromatography-mass spectrometry (GC-MS); however, a major challenge associated with GC-MS is the thermolytic degradation of substances with sensitive functional groups. Herein, we report the comprehensive thermal degradation and ester transformation of amide-based SCs, such as AB-FUBINACA, AB-CHMINACA, and MAB-CHMINACA, during GC-MS analysis and their treatment with analyte protectants (APs). These SCs were found to undergo thermolytic degradation during GC-MS in the presence of non-alcohol solvents. Using methanol as an injection solvent resulted in the conversion of the amide group to an ester group, producing other SCs such as AMB-FUBINACA, MA-CHMINACA, and MDMB-CHMINACA. Degradant and ester product formation has been interpreted as the adsorption of target SCs on glass wool via hydrogen bonding interactions between the active silanol and amide groups of the SCs, followed by an addition and/or elimination process. The factors found to influence the thermal degradation and/or esterification of the amide functional group include residence time, activity of glass wool, and injection volume. This report presents the fragmentation patterns of all compounds that were produced by degradation and esterification. Using 0.5 % sorbitol (AP) in MeOH as an injection solvent resulted in complete protection and improvement of the chromatographic shape of the compounds. This method has been successfully confirmed in terms of sensitivity, linearity, accuracy, and precision for standard solutions and tablet extraction using 0.5 % sorbitol in MeOH. Using AP increased the sensitivity by ten times or more compared to the use of only MeOH. The limit of detection for all analytes was determined as 25 ng/mL, and the calibration curves were linear over the concentration range of 50-2000 ng/mL. The values of accuracy error were below 11 %, and precision was less than 13 %. The effects of phytochemicals of herbal products, tablet ingredients, and biological matrices on the degradation and/or esterification and APs performance have also been evaluated in this work.
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Affiliation(s)
- Khaled Masoud Mohamed Masoud
- Forensic Chemistry Laboratory, Department of Forensic Sciences, Naif Arab University for Security Sciences, Riyadh, Saudi Arabia.
| | - Syed Mujeebuddin Syed
- Forensic Chemistry Laboratory, Department of Forensic Sciences, Naif Arab University for Security Sciences, Riyadh, Saudi Arabia
| | - Alanoud Mosa Alasiri
- Forensic Chemistry Laboratory, Department of Forensic Sciences, Naif Arab University for Security Sciences, Riyadh, Saudi Arabia
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2
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Bhartia B, Jayaraman S, Troadec C, Madapusi SP, Puniredd SR. Grafting of Organophosphonic Acid Monolayers on Hydrogen-Terminated Silicon Surface and Secondary Functionalization in Supercritical Carbon Dioxide Media. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:12063-12074. [PMID: 37581455 DOI: 10.1021/acs.langmuir.3c01278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/16/2023]
Abstract
The monolayer grafting on the oxide-free Si surface is challenging due to vulnerability of the surface against oxide formation in an ambient atmosphere. Most of the conventional studies focused on organic solvent-based chemistry and solvent and substrate interfaces, and residual solvents after the monolayer grafting play a key role in producing the highly stable monolayers. CO2 in its supercritical state (SCCO2) provides an elegant engineering solution for the problem faced as it can be used as inert processing environment and as carrier fluid for monolayer grafting taking up the role of organic solvents. In this work, monolayers of alkyl organophosphonic acids (OPAs) and functional OPAs were grafted on hydrogen-terminated oxide-free Si surfaces using the SCCO2 process. Grafted monolayers were physically and chemically characterized to verify the successful monolayer formation and determine the nature of the covalent binding configuration on the surface. To broaden the prospects of practical utility of the process and the OPA monolayer, the (3-bromopropyl)phosphonic acid (BPPA) monolayer was demonstrated to undergo secondary functionalization by terminal group substitution to convert the Br terminal group to the OH terminal group and secondary monolayer grafting to assemble 4-fluorothiophenol on top of the BPPA monolayer. The ability of monolayers to sustain secondary functionalization processing qualitatively hints toward ordered and stable monolayers of OPAs. The developed SCCO2 process in this work presents a single-step, green, and scalable method to graft the OPA monolayer on oxide-free Si which can employed in the future for monolayer doping, highly selective biochemical sensors, and targeted biological interactions.
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Affiliation(s)
- Bhavesh Bhartia
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, #08-3, Singapore 138634, Republic of Singapore
- Department of Chemical and Biomolecular Engineering, National University of Singapore,4 Engineering Drive 4, Singapore 117585, Republic of Singapore
| | - Sundaramurthy Jayaraman
- YSQ International Pte Ltd, 401 Commonwealth Drive, #07-01, Singapore 149598, Republic of Singapore
| | - Cedric Troadec
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, #08-3, Singapore 138634, Republic of Singapore
| | - Srinivasan Palavedu Madapusi
- Department of Chemical Engineering, BITS Pilani, Dubai Campus, Dubai International Academic City, P.O. Box No. 345055, Dubai 500001, UAE
| | - Sreenivasa Reddy Puniredd
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, #08-3, Singapore 138634, Republic of Singapore
- Singapore Institute of Food and Biotechnology Innovation (SIFBI), Agency for Science, Technology and Research (A*STAR), 31 Biopolis Way, Nanos, #01-02, Singapore 138669, Republic of Singapore
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3
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Reimers JR, Yang J, Darwish N, Kosov DS. Silicon - single molecule - silicon circuits. Chem Sci 2021; 12:15870-15881. [PMID: 35024111 PMCID: PMC8672724 DOI: 10.1039/d1sc04943g] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 10/28/2021] [Indexed: 12/23/2022] Open
Abstract
In 2020, silicon - molecule - silicon junctions were fabricated and shown to be on average one third as conductive as traditional junctions made using gold electrodes, but in some instances to be even more conductive, and significantly 3 times more extendable and 5 times more mechanically stable. Herein, calculations are performed of single-molecule junction structure and conductivity pertaining to blinking and scanning-tunnelling-microscopy (STM) break junction (STMBJ) experiments performed using chemisorbed 1,6-hexanedithiol linkers. Some strikingly different characteristics are found compared to analogous junctions formed using the metals which, to date, have dominated the field of molecular electronics. In the STMBJ experiment, following retraction of the STM tip after collision with the substrate, unterminated silicon surface dangling bonds are predicted to remain after reaction of the fresh tips with the dithiol solute. These dangling bonds occupy the silicon band gap and are predicted to facilitate extraordinary single-molecule conductivity. Enhanced junction extendibility is attributed to junction flexibility and the translation of adsorbed molecules between silicon dangling bonds. The calculations investigate a range of junction atomic-structural models using density-functional-theory (DFT) calculations of structure, often explored at 300 K using molecular dynamics (MD) simulations. These are aided by DFT calculations of barriers for passivation reactions of the dangling bonds. Thermally averaged conductivities are then evaluated using non-equilibrium Green's function (NEGF) methods. Countless applications through electronics, nanotechnology, photonics, and sensing are envisaged for this technology.
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Affiliation(s)
- Jeffrey R Reimers
- International Centre for Quantum and Molecular Structures and School of Physics, Shanghai University Shanghai 200444 China
- School of Mathematical and Physical Sciences, University of Technology Sydney NSW 2007 Australia
| | - Junhao Yang
- International Centre for Quantum and Molecular Structures and School of Physics, Shanghai University Shanghai 200444 China
| | - Nadim Darwish
- School of Molecular and Life Sciences, Curtin Institute of Functional Molecules and Interfaces, Curtin University Bentley WA 6102 Australia
| | - Daniel S Kosov
- College of Science and Engineering, James Cook University Townsville QLD 4811 Australia
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4
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Hladík M, Fejfar A, Vázquez H. Doping of the hydrogen-passivated Si(100) electronic structure through carborane adsorption studied using density functional theory. Phys Chem Chem Phys 2021; 23:20379-20387. [PMID: 34491256 DOI: 10.1039/d1cp01654g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Adsorption of molecular materials with tailored chemical properties represents a new and promising avenue to non-destructively dope silicon. Dithiocarboranes possess large permanent dipoles and readily form stable monolayers on a variety of substrates. Here we use density functional theory to investigate the doping of hydrogen-passivated Si(100) substrates through the adsorption of dithiocarborane molecules. We find that dithiocarboranes can both physisorb and chemisorb on the substrate. Chemisorbed structures arise when a S atom in the molecular linker group replaces a surface H atom. We establish the formation of these Si-molecule bonds and characterize their mechanical and thermal stability. Analysis of the calculated electronic structure of adsorbed interfaces shows that carborane adsorption does not result in interface gap states. The band gap in adsorbed junctions is defined by Si states and its magnitude is almost unchanged with respect to the clean Si slab. The large carborane electrostatic dipole results in the downwards shift of Si spectral features by 0.3 eV, reducing the hole injection barrier by this amount with respect to the pristine Si substrate. Molecular dynamics simulations reveal these structural and electronic features to be stable at room temperature. Our work shows that molecular adsorbates having large electrostatic dipoles are a promising strategy to non-destructively dope semiconductor substrates.
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Affiliation(s)
- Martin Hladík
- Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00 Prague, Czech Republic.
| | - Antonín Fejfar
- Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00 Prague, Czech Republic.
| | - Héctor Vázquez
- Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00 Prague, Czech Republic.
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5
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Peiris CR, Ciampi S, Dief EM, Zhang J, Canfield PJ, Le Brun AP, Kosov DS, Reimers JR, Darwish N. Spontaneous S-Si bonding of alkanethiols to Si(111)-H: towards Si-molecule-Si circuits. Chem Sci 2020; 11:5246-5256. [PMID: 34122981 PMCID: PMC8159313 DOI: 10.1039/d0sc01073a] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We report the synthesis of covalently linked self-assembled monolayers (SAMs) on silicon surfaces, using mild conditions, in a way that is compatible with silicon-electronics fabrication technologies. In molecular electronics, SAMs of functional molecules tethered to gold via sulfur linkages dominate, but these devices are not robust in design and not amenable to scalable manufacture. Whereas covalent bonding to silicon has long been recognized as an attractive alternative, only formation processes involving high temperature and/or pressure, strong chemicals, or irradiation are known. To make molecular devices on silicon under mild conditions with properties reminiscent of Au–S ones, we exploit the susceptibility of thiols to oxidation by dissolved O2, initiating free-radical polymerization mechanisms without causing oxidative damage to the surface. Without thiols present, dissolved O2 would normally oxidize the silicon and hence reaction conditions such as these have been strenuously avoided in the past. The surface coverage on Si(111)–H is measured to be very high, 75% of a full monolayer, with density-functional theory calculations used to profile spontaneous reaction mechanisms. The impact of the Si–S chemistry in single-molecule electronics is demonstrated using STM-junction approaches by forming Si–hexanedithiol–Si junctions. Si–S contacts result in single-molecule wires that are mechanically stable, with an average lifetime at room temperature of 2.7 s, which is five folds higher than that reported for conventional molecular junctions formed between gold electrodes. The enhanced “ON” lifetime of this single-molecule circuit enables previously inaccessible electrical measurements on single molecules. Spontaneously formed Si–S bonds enable monolayer and single-molecule Si–molecule–Si circuits.![]()
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Affiliation(s)
- Chandramalika R Peiris
- School of Molecular and Life Sciences, Curtin Institute of Functional Molecules and Interfaces, Curtin University Bentley WA 6102 Australia
| | - Simone Ciampi
- School of Molecular and Life Sciences, Curtin Institute of Functional Molecules and Interfaces, Curtin University Bentley WA 6102 Australia
| | - Essam M Dief
- School of Molecular and Life Sciences, Curtin Institute of Functional Molecules and Interfaces, Curtin University Bentley WA 6102 Australia
| | - Jinyang Zhang
- School of Molecular and Life Sciences, Curtin Institute of Functional Molecules and Interfaces, Curtin University Bentley WA 6102 Australia
| | - Peter J Canfield
- International Centre for Quantum and Molecular Structures, School of Physics, Shanghai University Shanghai 200444 China.,School of Chemistry, The University of Sydney NSW 2006 Australia
| | - Anton P Le Brun
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organization (ANSTO) Lucas Heights NSW 2234 Australia
| | - Daniel S Kosov
- College of Science and Engineering, James Cook University Townsville QLD 4811 Australia
| | - Jeffrey R Reimers
- International Centre for Quantum and Molecular Structures, School of Physics, Shanghai University Shanghai 200444 China.,School of Mathematical and Physical Sciences, University of Technology Sydney NSW 2007 Australia
| | - Nadim Darwish
- School of Molecular and Life Sciences, Curtin Institute of Functional Molecules and Interfaces, Curtin University Bentley WA 6102 Australia
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6
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Kang J, Sim S, Jung H, Han B, Lee YW. Desulfurization of hexyl sulfide and hexanethiol using supercritical water. J Supercrit Fluids 2020. [DOI: 10.1016/j.supflu.2019.104734] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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7
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Two-dimensional Electron Gas at Thiol/ZnO Interface. E-JOURNAL OF SURFACE SCIENCE AND NANOTECHNOLOGY 2020. [DOI: 10.1380/ejssnt.2020.41] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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8
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Chang LY, Kuo YC, Shiu HW, Wang CH, Lee YC, Yang YW, Gwo S, Chen CH. n-Alkanethiols Directly Grown on a Bare Si(111) Surface: From Disordered to Ordered Transition. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:14244-14251. [PMID: 29148786 DOI: 10.1021/acs.langmuir.7b03302] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We observed the growth phase transition of n-alkanethiols (AT), CH3(CH2)n-1SH, n = 4-16, directly implanted on a bare Si(111) surface, forming an AT monolayer. These monolayers were characterized with static water-contact angle, high-resolution X-ray photoelectron spectroscopy, near-edge X-ray fine-structure spectroscopy, and grazing-angle reflection absorption Fourier-transform infrared spectroscopy. The integrated spectral results indicated that the implanted n-AT molecules formed a self-oriented and densely packed monolayer through formation of an S-Si bond. With the number of carbons in the alkyl chain at six or more, namely beginning at hexanethiol, the molecular monolayer began to develop an orientation-ordered structure, which is clearly shorter than that for AT monolayers on Au and Ag. This result implies that, with a stronger molecule-substrate interaction, an ordered molecular monolayer can form with a short chain.
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Affiliation(s)
- Lo Yueh Chang
- National Synchrotron Radiation Research Center , Hsinchu, 30076, Taiwan
- Department of Physics, National Tsing Hua University , Hsinchu 30013, Taiwan
| | - Yen-Chien Kuo
- National Synchrotron Radiation Research Center , Hsinchu, 30076, Taiwan
| | - Hung Wei Shiu
- National Synchrotron Radiation Research Center , Hsinchu, 30076, Taiwan
| | - Chia-Hsin Wang
- National Synchrotron Radiation Research Center , Hsinchu, 30076, Taiwan
| | - Yao-Chang Lee
- National Synchrotron Radiation Research Center , Hsinchu, 30076, Taiwan
| | - Yaw-Wen Yang
- National Synchrotron Radiation Research Center , Hsinchu, 30076, Taiwan
| | - Shangjr Gwo
- National Synchrotron Radiation Research Center , Hsinchu, 30076, Taiwan
- Department of Physics, National Tsing Hua University , Hsinchu 30013, Taiwan
| | - Chia-Hao Chen
- National Synchrotron Radiation Research Center , Hsinchu, 30076, Taiwan
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9
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Bhartia B, Puniredd SR, Jayaraman S, Gandhimathi C, Sharma M, Kuo YC, Chen CH, Reddy VJ, Troadec C, Srinivasan MP. Highly Stable Bonding of Thiol Monolayers to Hydrogen-Terminated Si via Supercritical Carbon Dioxide: Toward a Super Hydrophobic and Bioresistant Surface. ACS APPLIED MATERIALS & INTERFACES 2016; 8:24933-24945. [PMID: 27540859 DOI: 10.1021/acsami.6b06018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Oxide-free silicon chemistry has been widely studied using wet-chemistry methods, but for emerging applications such as molecular electronics on silicon, nanowire-based sensors, and biochips, these methods may not be suitable as they can give rise to defects due to surface contamination, residual solvents, which in turn can affect the grafted monolayer devices for practical applications. Therefore, there is a need for a cleaner, reproducible, scalable, and environmentally benign monolayer grafting process. In this work, monolayers of alkylthiols were deposited on oxide-free semiconductor surfaces using supercritical carbon dioxide (SCCO2) as a carrier fluid owing to its favorable physical properties. The identity of grafted monolayers was monitored with Fourier transform infrared (FTIR) spectroscopy, high-resolution X-ray photoelectron spectroscopy (HRXPS), XPS, atomic force microscopy (AFM), contact angle measurements, and ellipsometry. Monolayers on oxide-free silicon were able to passivate the surface for more than 50 days (10 times than the conventional methods) without any oxide formation in ambient atmosphere. Application of the SCCO2 process was further extended by depositing alkylthiol monolayers on fragile and brittle 1D silicon nanowires (SiNWs) and 2D germanium substrates. With the recent interest in SiNWs for biological applications, the thiol-passivated oxide-free silicon nanowire surfaces were also studied for their biological response. Alkylthiol-functionalized SiNWs showed a significant decrease in cell proliferation owing to their superhydrophobicity combined with the rough surface morphology. Furthermore, tribological studies showed a sharp decrease in the coefficient of friction, which was found to be dependent on the alkyl chain length and surface bond. These studies can be used for the development of cost-effective and highly stable monolayers for practical applications such as solar cells, biosensors, molecular electronics, micro- and nano- electromechanical systems, antifouling agents, and drug delivery.
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Affiliation(s)
- Bhavesh Bhartia
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, #08-32, Singapore 138634
- Department of Chemical and Biomolecular Engineering, National University of Singapore , 4 Engineering Drive 4, Singapore 117585
| | - Sreenivasa Reddy Puniredd
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, #08-32, Singapore 138634
| | - Sundaramurthy Jayaraman
- Environmental and Water Technology Centre of Innovation, Ngee Ann Polytechnic , 535 Clementi Road, Singapore 599489
| | - Chinnasamy Gandhimathi
- Centre for Nanofibers and Nanotechnology, Nanoscience and Nanotechnology Initiative, National University of Singapore , Singapore 117576
| | - Mohit Sharma
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, #08-32, Singapore 138634
| | - Yen-Chien Kuo
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Chia-Hao Chen
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Venugopal Jayarama Reddy
- Centre for Nanofibers and Nanotechnology, Nanoscience and Nanotechnology Initiative, National University of Singapore , Singapore 117576
| | - Cedric Troadec
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, #08-32, Singapore 138634
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10
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Buriak JM, Sikder MDH. From Molecules to Surfaces: Radical-Based Mechanisms of Si–S and Si–Se Bond Formation on Silicon. J Am Chem Soc 2015; 137:9730-8. [DOI: 10.1021/jacs.5b05738] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jillian M. Buriak
- Department
of Chemistry, University of Alberta, and the National Institute for Nanotechnology, Edmonton, AB T6G 2G2, Canada
| | - Md Delwar H. Sikder
- Department
of Chemistry, University of Alberta, and the National Institute for Nanotechnology, Edmonton, AB T6G 2G2, Canada
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11
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Yang LK, Su YQ, Wu XY, Zhang DX, Chen YL, Yang FZ, Wu DY, Tian ZQ. White-light induced grafting of 3-MPA on the Si(111)-H surface for catalyzing Au nanoparticles' in situ growth. NANOSCALE 2015; 7:9563-9569. [PMID: 25947616 DOI: 10.1039/c5nr00664c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A novel, mild and effective method was designed for grafting of high-quality organic monolayers on a silicon surface to catalyze nanoparticles' growth. By using a white-light source, 3-mercaptopropionic acid (3-MPA) molecules were attached to hydrogen-terminated Si(111) surfaces at room temperature. The attached monolayers were characterized using X-ray photoelectron spectroscopy to provide detailed information. The in situ growth of Au nanoparticles (AuNPs) with dimensions below 20 nm was catalyzed on a silicon surface with highly uniform and compact structure morphology. The AuNPs can grow selectively in a certain region on a patterned Si-Si3N4 chip. p-Nitrothiophenol (p-NTP) was used as the probe to evaluate the SERS enhancement of the highly uniform and compact AuNP-Si substrate. In order to better understand the white light initiation of the addition reaction of 3-MPA on the Si(111)-H surface, the mechanism was elucidated by density functional theoretical (DFT) calculations, which indicated that the formation of the Si-O bond occurred at the PEC of the first singlet excited state (S1) with a very low activation barrier about 30% of the ground state (S0) value.
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Affiliation(s)
- Li-Kun Yang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
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12
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Cho J, Choi CH. Thermal decomposition mechanisms of methylamine, ethylamine, and 1-propylamine on Si(100)-2 × 1 surface. J Chem Phys 2011; 134:194701. [PMID: 21599076 DOI: 10.1063/1.3589362] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The thermal decomposition reactions of methylamine, ethylamine, and 1-propylamine absorbed on Si(100)-2 × 1 surface were theoretically investigated. Eight decomposition channels were found leading to desorption products of imine, H(2), alkyl cyanide, ammonia, aziridine, alkene, azetidine, and cyclopropane, which supports the experimental assignments. Our mechanistic studies strongly suggest that the alkyl cyanide (hydrogen cyanide in the case of methylamine) channel is coupled with the hydrogen desorption step. The β-hydrogen of ethylamine and 1-propylamine was found to undergo additional decomposition reactions producing aziridine and alkene, which were classified as γ- and β-eliminations, respectively. It was also found that the γ-hydrogen of 1-propylamine undergoes azetidine and cyclopropane producing decompositions, which were classified as δ- and γ-eliminations. In general, γ- and δ-hydrogen involved decomposition reactions are kinetically less favorable than β-hydrogen involved ones. Consequently, it is expected that the thermal decompositions of the primary alkyl amines with longer alkyl chains would not add additional favorable decomposition channels. Except alkyl cyanide and ammonia desorption channels, the decompositions occur in a concerted fashion.
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Affiliation(s)
- Jieun Cho
- Department of Chemistry and Green-Nano Materials Research Center, College of Natural Sciences, Kyungpook National University, Taegu 702-701, South Korea
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13
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Lou JL, Shiu HW, Chang LY, Wu CP, Soo YL, Chen CH. Preparation and characterization of an ordered 1-dodecanethiol monolayer on bare Si(111) surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:3436-41. [PMID: 21401112 DOI: 10.1021/la103585t] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
We have grown 1-dodecandthiol (DDT) monolayer on a bare Si(111) surface through ultraviolet-assisted photochemical reaction. The resulting monolayer was investigated by means of water contact angle measurement, synchrotron radiation-based high-resolution X-ray photoelectron spectroscopy, and polarization-dependent near-edge X-ray absorption fine structure spectroscopy. These combined probes for characterization reveal a hydrophobic ambient surface; the DDT was directly attached to Si through a Si-S bond, and the molecules formed an ordered monolayer with an average tilt angle of 57° of the alkyl chains relative to the substrate surface.
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Affiliation(s)
- Jie Ling Lou
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
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14
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Kachian JS, Wong KT, Bent SF. Periodic trends in organic functionalization of group IV semiconductor surfaces. Acc Chem Res 2010; 43:346-55. [PMID: 20041705 DOI: 10.1021/ar900251s] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Organic functionalization of group IV semiconductor surfaces provides a means to precisely control the interfacial properties of some of the most technologically important electronic materials in use today. The 2 x 1 reconstructed group IV (100) surfaces in ultrahigh vacuum, in particular, have a well-defined surface that allows adsorbate-surface interactions to be studied in detail. Surface dimers containing a strong sigma- and weak pi-bond form upon reconstruction of the group IV (100) surfaces, imparting a rich surface reactivity, which allows useful analogies to be made between reactions at the surface and those in classic organic chemistry. To date, most studies have focused on single substrates and a limited number of adsorbate functional groups. In this Account, we bring together experimental and theoretical results from several studies to investigate broader trends in thermodynamics and kinetics of organic molecules reacted with group IV (100)-2 x 1 surfaces. By rationalizing these trends in terms of simple periodic properties, we aim to provide guidelines by which to understand the chemical origin of the observed trends and predict how related molecules or functionalities will react. Results of experimental and theoretical studies are used to show that relative electronegativities and orbital overlap correlate well with surface-adsorbate covalent bond strength, while orbital overlap together with donor electronegativity and acceptor electron affinity correlate with surface-adsorbate dative bond strength. Using such simple properties as predictive tools is limited, of course, but theoretical calculations fill in some of the gaps. The predictive power inherent in periodic trends may be put to use in designing molecules for applications where controlled attachment of organic molecules to semiconductor surfaces is needed. Organic functionalization may facilitate the semiconductor industry's transition from traditional silicon-based architectures to other materials, such as germanium, that offer better electrical properties. Potential applications also exist in other fields ranging from organic and molecular electronics, where control of interfacial properties may allow coupling of traditional semiconductor technology with such developing technologies, to biosensors and nanoscale lithography, where the functionality imparted to the surface may be used directly. Knowledge of thermodynamic and kinetic trends and the fundamental basis of these trends may enable effective development of new functionalization strategies for such applications.
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Affiliation(s)
- Jessica S. Kachian
- Department of Chemical Engineering, Stanford University, Stanford, California 94305
| | - Keith T. Wong
- Department of Chemical Engineering, Stanford University, Stanford, California 94305
| | - Stacey F. Bent
- Department of Chemical Engineering, Stanford University, Stanford, California 94305
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15
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Kachian JS, Bent SF. Sulfur versus Oxygen Reactivity of Organic Molecules at the Ge(100)-2×1 Surface. J Am Chem Soc 2009; 131:7005-15. [DOI: 10.1021/ja808066t] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jessica S. Kachian
- Department of Chemical Engineering, Stanford University, Stanford, California 94305
| | - Stacey F. Bent
- Department of Chemical Engineering, Stanford University, Stanford, California 94305
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Lin TH, Huang TP, Liu YL, Yeh CC, Lai YH, Hung WH. Adsorption and Thermal Reactions of Alkanethiols on Pt(111): Dependence on the Length of the Alkyl Chain. J Phys Chem B 2005; 109:14079-84. [PMID: 16852768 DOI: 10.1021/jp058084r] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The adsorption and thermal decomposition of alkanethiols (R-SH, where R = CH3, C2H5, and C4H9) on Pt(111) were studied with temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) with synchrotron radiation. Dissociation of sulfhydryl hydrogen (RS-H) of alkanethiol results in the formation of alkanethiolate; the extent of dissociation at an adsorption temperature of 110 K depends on the length of the alkyl chain. At small exposure, all chemisorbed CH3SH, C2H5SH, and C4H9SH decompose to desorb hydrogen below 370 K and yield carbon and sulfur on the surface. Desorption of products containing carbon is observed only at large exposure. In thermal decomposition, alkanethiolate is proposed to undergo a stepwise dehydrogenation: R'-CH2S --> R'-CHS --> R'-CS, R' = H, CH3, and C3H7. Further decomposition of the R'-CS intermediate results in desorption of H2 at 400-500 K and leaves carbon and sulfur on the surface. On the basis of TPD and XPS data, we conclude that the density of adsorption of alkanethiol decreases with increasing length of the alkyl chain. C4H9SH is proposed to adsorb mainly with a configuration in which its alkyl group interacts with the surface; this interaction diminishes the density of adsorption of alkanethiols but facilitates dehydrogenation of the alkyl group.
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Affiliation(s)
- T H Lin
- Department of Chemistry, National Taiwan Normal University, Taipei 116, Taiwan
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Donev S, Brack N, Paris NJ, Pigram PJ, Singh NK, Usher BF. Surface reactions of 1-propanethiol on GaAs(100). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:1866-1874. [PMID: 15723483 DOI: 10.1021/la048191x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The adsorption and decomposition pathways of 1-propanethiol on a Ga-rich GaAs(100) surface have been investigated using the techniques of temperature programmed desorption, X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (TOF-SIMS). 1-Propanethiol adsorbs dissociatively on a clean GaAs(100) surface to form propanethiolate and hydrogen. Further reactions of these species to form new products compete with the recombinative desorption of molecular propanethiol. The C-S bond scission in the propanethiolate results in the formation of propyl species and elemental sulfur. The generation of propene via beta-hydride elimination then follows. In addition, propane and hydrogen form via reductive elimination processes. A recombinative high-temperature propanethiol desorption state is also observed. XPS and TOF-SIMS analyses confirm the presence of sulfur on the GaAs(100) surface following thermal decomposition. This paper discusses the mechanisms by which these products form on the GaAs(100) surface.
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Affiliation(s)
- Suzy Donev
- Centre for Materials and Surface Science, La Trobe University, Melbourne, Victoria 3086, Australia
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